A conventionally ridged grinding wheel initially contacts a work piece at the outer most portion of the ridges of the grinding surface. Since there is no contact between the valley portions of the grinding wheel and the work piece until the work piece has been ground to a substantial depth by the ridges, the ridges are subjected to wear during the entire grinding operation, whereas the valley portions are subject to wear only after grinding of the work piece is substantially completed. This action normally causes rapid wear of the ridges resulting in a consequent necessity for frequent re-dressing of the grinding wheel. Wear of the ridges causes them to lose their desired shape, requiring frequent redressing of the wheel if a particular configuration of the ridges is essential.
It is well known to produce a series of scallops or grooves, commonly called serrations, along knife edges and similar articles, by means of grinding wheels having a surface configuration complementary to the final shape of the serrations in the knife. Heretofore, the expense of frequent re-dressing to restore the desired shape of the ridges of the grinding wheel has been substantial, to such an extent that the cost has frequently precluded the use of serrations or other grooved surfaces or edges where they would be desirable.
It is well known that the common cylindrical surface of a grinding wheel normally becomes convexly arched with continued use and must be dressed from time to time in order to restore the desired cylindrical grinding surface. With grinding wheels having a series of circumferential ridges along their grinding surface, the ridges flatten out during use. Upon continued use of the wheel the entire grinding surface begins to arch convexly. Thus, such ridged wheels must be frequently re-dressed to restore the desired configuration of the ridges.
A "Tooling Device for Stone and the Like" is shown in a patent granted in 1911, U.S. Pat. No. 1,000,813, in which a series of abrasive discs are mounted on a rotary shaft, each of the discs having a convexly arched grinding surface which together form a corrugated or crimped surface for providing a fluted surface on a work piece such as a stone, to resemble a tooling effect. During continued use of the assembled discs, the ridges will be flattened and it will be necessary to re-dress the discs in order to obtain the desired tooling effect.
A "Sharpening Device for Bush Hammers" is shown in a 1912 patent, U.S. Pat. No. 1,045,016. A series of convexly beveled, V-shaped grinding surfaces are spaced slightly apart by paper discs and are clamped together by wooden discs at either end, the wooden discs being clamped between a nut and a stop collar held by a set screw. Aside from the series of discs being likely to loosen, the V-shaped ridges will lose their points and the abrasive segments will become arched so that re-dressing will be required. Also, the paper discs are likely to be ripped apart when engaged by the points formed on the work piece during the grinding operation.
A cylindrical surfaced grinding wheel having an annular groove is shown in a 1946 patent, U.S. Pat. No. 2,396,505. The stated function of the groove is to relieve stresses during grinding of a resilient work piece and to equalize wear of the grinding surfaces. Typically, the cylindrical grinding surfaces can be expected to become arched during continued use. The wheel is manufactured by filling one half of a cylindrical mold and then placing a pair of semi-cylindrical metal spacing plates on top of the abrasive fill, then filling the rest of the mold with the abrasive fill and pressing the abrasive fill. Finally, the semi-cylindrical plates may be removed, thus forming the groove.
"Grinding or Polishing Rollers for Glass and the Like" is shown in a British patent accepted in 1926, British Pat. No. 261,227, in which cylindrical cast iron or Carborundum rollers, or the like, are provided with grooves. The grooves are not filled and are intended to permit water to flow away from the cylindrical surfaces for removing grinding or polishing substances.
Additional patents of a generally related nature include: U.S. Ser. No. 925,546; U.S. Pat. Nos.: 1,963,154, 1,975,070, 1,984,936, 2,079,787, 2,467,596 and 2,705,194.